focus- the point under Earth's surface where rock that is under stress breaks and creates an earthquake.
epicenter- the point directly beneath the focus, which gets the most severe damage when an earthquake happens.
seismic waves- vibrations that travel through the Earth carrying energy released from an earthquake.
primary waves- also called "P- waves", these waves are the first waves to arrive. P- waves are earthquake waves that compress and expand the ground, stretching the Earth's crust like an accordion being played.
secondary waves also called "S- waves", these waves are second to arrive (primary waves being the first). S waves are waves that vibrate side by side as well as up and down. Unlike P- waves, which can through liquids as well as solids, S- waves cannot pass through liquids.
surface waves- after P- waves and S- waves reach the surface, some of them turn into surface waves. Although they move slower than P- waves and S- waves, they create the most serious ground movements.
Magnitude- a measurement of earthquake strength based on seismic waves around faults.
Mercalli Scale- A scale developed to rate earthquakes based on their intensity.
Richter Scale- A scale that is based on the size of the seismic waves as recorded by a seismograph.
Moment Magnitude Scale- A scale that estimates the total energy released by an earthquake, near or far, big or small.
Outline
T= Measuring Earthquakes
focus
place where rock breaks
epicenter
place directly above the focus
most severe shaking in earthquake
1. Seismic Waves
The fault, the epicenter, the focus and seimic waves
Table of Contents
Vocabulary
focus- the point under Earth's surface where rock that is under stress breaks and creates an earthquake.
epicenter- the point directly beneath the focus, which gets the most severe damage when an earthquake happens.
seismic waves- vibrations that travel through the Earth carrying energy released from an earthquake.
primary waves- also called "P- waves", these waves are the first waves to arrive. P- waves are earthquake waves that compress and expand the ground, stretching the Earth's crust like an accordion being played.
secondary waves also called "S- waves", these waves are second to arrive (primary waves being the first). S waves are waves that vibrate side by side as well as up and down. Unlike P- waves, which can through liquids as well as solids, S- waves cannot pass through liquids.
surface waves- after P- waves and S- waves reach the surface, some of them turn into surface waves. Although they move slower than P- waves and S- waves, they create the most serious ground movements.
Magnitude- a measurement of earthquake strength based on seismic waves around faults.
Mercalli Scale- A scale developed to rate earthquakes based on their intensity.
Richter Scale- A scale that is based on the size of the seismic waves as recorded by a seismograph.
Moment Magnitude Scale- A scale that estimates the total energy released by an earthquake, near or far, big or small.
Outline
T= Measuring Earthquakes
- focus
- place where rock breaks
- epicenter
- place directly above the focus
- most severe shaking in earthquake
- 1. Seismic Waves
The fault, the epicenter, the focus and seimic waves
- vibrations that travel through earth
- carrying energy released from earthquake
- carry the energy of earthquake
- away from the focus
- through Earth's interior
- and across the surface
- energy released= greatest at epicenter
- three types of seismic waves
- P- waves
- S- waves
- surface wave
1. primary Waves- also p- waves
- waves that compress + expand ground
- can cause buildings to expand and contract
1. secondary waves- waves rock up+ down, side+ side
- shake structures violently
- cannot go through liquids
1. surface waves- when p- waves, s- waves reach surface
- some become surface waves
- slower than P- waves, S- waves
- make most severe ground movement
- some roll like ocean waves
- some shake from side to side
1. Detecting Seismic Waves- Seismographs used to find waves
- record ground movement
- built by wire attached to pen
- on a piece of paper
- pen shakes, and paper records it
- bigger the waves on paper, bigger earthquake
1. Measuring Earthquakes- Three ways of measuring earthquakes
- Mercalli Scale
- Richter Scale
- Moment Magnitude Scale
- magnitude
- measurement of earthquake strength
- based on seismic waves
- and movement of fault
- The Mecalli Scale
- rate earthquakes by intensity
- intensity= strength of ground motion
- not a precise measurement
- 12 steps
- The Richter Scale
- rating size of seismic waves
- based on seismograph
- accurate measurements for nearby, earthquakes
- inaccurate for big, distant earthquakes
- The Moment Magnitude Scale
- Used by geologists today
- rate earthquakes big or small
- near or far
- 5.0= little damage
- above 5.0= big destruction
1. Locating the Epicenter*
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